The SSM serves two purposes:
1. It provides estimates for the helium abundance and mixing length parameter by forcing the stellar model to have the correct luminosity and radius at the Sun's age,
2. It provides a way to evaluate more complex models with additional physics, such as rotation, magnetic fields and diffusion or improvements to the treatment of convection, such as modelling turbulence, and convective overshooting.
Like the Standard Model of particle physics and the standard cosmology model the SSM changes over time in response to relevant new theoretical or experimental physics discoveries.
Unfortunately the SSM is incorrect in many, many ways. To combat bad physics, we must first correct the points given above:
1. The Sun's age is incorrect, it is a young, not old star. They forced the stellar model to have correct luminosity, this means the original stellar model was actually much dimmer (it had stars as not shining, but in all actuality it has stars as still not shining, as they are static systems not exchanging heat with their environment, astronomers and astrophysicists just gloss over this embarrassing fact.)
2. Having more complex models is horrendous. Good science is simple. The model stellar metamorphosis provides is a star of hollow structure which collapses on itself as it ages and cools becoming the "planet", all the while differentiating the interior.
Like the standard model of particle physics and the standard cosmology model, the SSM is full of ad hoc assumptions, is absolutely incorrect and needs to be replaced.